1. Field of the Invention
The present invention relates to a screen printing apparatus.
2. Description of the Conventional Art
A conventional screen printing apparatus is, for example, as shown in FIGS. 11(a)-11(d), constituted by a base plate 101 on which a substrate to be printed 102 is mounted, and a screen printing plate 103 provided in a tensional manner on the base plate 101 is substantially parallel to an upper surface of the base plate, and is structured such as to pass a printing paste 105 supplied on the screen printing plate 103 by a paste supplying means 106 in a manner shown in FIG. 11(a) through a pattern hole (not shown) of the screen printing plate 103 due to a movement of a squeegee 104 as shown in FIG. 11(b), thereby forming a pattern on the substrate to be printed 102. In this case, FIG. 11(c) is a view showing a state that a movement of the squeegee reaches a terminal end, and FIG. 11(d) is a view showing a state of moving the squeegee in an opposite direction so as to start printing.
In this case, in order to stably executed the screen printing, it is necessary to control a viscosity of the paste, a performance of the screen printing plate (a thickness of the screen printing plate, a tension balance, an accuracy, a strength, a service life and the like), a performance of the squeegee (an accuracy, a hardness, an angle and the like), a mechanical performance (an accuracy, a speed control and a pressure control) and the like so as to always keep in a uniform state.
However, in the conventional screen printing apparatus mentioned above, since the paste 105 is applied to all over the screen printing plate 103 in an exposed manner, the following problems are provided.
{circle around (1)} Since a lot of expensive paste which costs between some tens of thousand yen and some hundreds of thousand yen is left on the screen printing plate, a lot of loss money is generated.
{circle around (2)} Since the paste is directly supplied onto the screen printing plate, a lot of time is required for changing the paste, so that an operation efficiency is largely reduced.
{circle around (3)} Since the paste is exposed to an air so as to be oxidized and a property is deteriorated, an electric property and the like after printing are deteriorated.
{circle around (4)} Since a solvent mixed in the paste is evaporated and the viscosity is changed, a printing property is significantly deteriorated.
{circle around (5)} Since the evaporated solvent has a strong odor, a problem relating to an environment pollution is generated.
{circle around (6)} Since the viscosity of the paste is changed due to an influence of a temperature change, a printing performance is significantly deteriorated.
{circle around (7)} Since dusts are mixed within the paste, the pattern formed by the printing is disconnected and shorted. Then, in order to carry out a countermeasure thereof, a clean room which is expensive and hard to be controlled is required.
Further, in order to solve the problem mentioned above, in Japanese Unexamined Patent Publication No. 6-210829, as shown in FIG. 12, there is proposed a method of charging a printing paste 205 within a chamber 209, supplying and recovering the paste 205 through a supply port 207 which can be opened and closed, by rotating a roller 206, and printing by a front blade 208. In this case, reference numeral 202 denotes a substrate to be printed, reference numeral 203 denotes a screen printing plate and reference numeral 204 denotes a rear blade.
However, in this method, the following problems are provided.
{circle around (1)} Since the paste is supplied due to a rotational force of the roller 206, it is necessary that the roller 206 and the paste are directly in contact with each other, so that a lot of time is required for cleaning and maintaining the roller.
{circle around (2)} Since the paste 205 is directly supplied within the chamber 209, it is necessary to carry out a maintenance such as a periodical cleaning or the like, so that a long time is required for the maintenance operation.
{circle around (3)} Since the paste 205 is directly supplied within the chamber 209, a lot of time is required for changing the paste, so that an operation efficiency is largely reduced.
{circle around (4)} Since a lot of expensive paste which costs between some tens of thousand yen and some hundreds of thousand yen per 1 kg is left within the chamber 209, a lot of loss money is generated.
{circle around (5)} Since an air is mixed at a time of supplying the paste 205 within the chamber 209, a defect such as a wire disconnection, a chip or the like is generated in a pattern after printing.
{circle around (6)} Since an inner portion of the chamber 209 is exposed to the air, the paste is oxidized or deteriorated.
{circle around (7)} It is necessary to control an elastic force of the squeegee, a wetting property of a surface of the squeegee and the like in correspondence to a property of the paste, however, in this example, since the squeegee is executed by the front blade 208 constituted by a thin plate metal, it is possible to adjust only on the basis of the metal, so that it is impossible to adjust a suitable elastic force.
The present invention is made by taking the points mentioned above into consideration, and an object of the present invention is to provide a screen printing apparatus which can always keep a printing paste in a uniform state, can print stably at a high accuracy, and can use an expansive paste with no waste, whereby it is possible to solve all of the problems mentioned above.
A screen printing apparatus provided with a means for solving the problem mentioned above is as follows.
(1) A screen printing apparatus for pattern-forming of a printing paste on a screen printing plate onto a substrate to be printed by moving a squeegee in a predetermined direction, comprising:
a bag-like container in which the printing paste is charged;
a mechanism for receiving the bag-like container and pressurizing the bag-like container;
a printing paste supply plate provided with a printing paste supply port; and
an elastic squeegee in which a back surface is formed at a fixed angle corresponding to an angle at a time of printing and a front surface is integrally formed with a hard thin plate,
wherein the mechanism for pressurizing the bag-like container is connected to the back surface side of the printing paste supply plate, the back surface of the squeegee is brought into contact with the printing paste supply port in the front surface side of the printing paste supply plate, and the screen printing apparatus is provided with a printing paste supply mechanism capable of being opened and closed through a vertical movement so as to supply a predetermined amount of printing paste, and a scraper for scraping up the printing paste on the screen printing plate.
(2) A screen printing apparatus for pattern-forming of a printing paste on a screen printing plate onto a substrate to be printed by moving a squeegee in a predetermined direction, comprising:
a step of moving upward the squeegee so as to open a printing paste supply port;
a step of pressurizing a container in which the printing paste is charged so as to supply a predetermined amount of printing paste;
a step of moving downward the squeegee after supplying the predetermined amount of printing paste so as to close the printing paste supply port and simultaneously arranging the squeegee on a screen printing plate;
a step of printing with the hard thin plate side of the elastic squeegee in which a front surface is integrally formed by a hard thin plate; and
a step of scraping up the printing paste on the screen printing plate by a scraper after printing, whereby the printing is carried out by repeating these steps.
(3) A screen printing apparatus in which a bag-like container charged with a printing paste is manufactured by a step of welding three peripheral portions, a step of cutting an inner side of one end among three welded portions, a step of again welding a closest outer side in the cut portion, a step of bonding the cut portion by an adhesive tape, a step of charging the paste, and a step of welding the remaining peripheral one, the bag-like container charged with the printing paste is inserted to a cartridge and set in the screen printing apparatus together with the cartridge, and the printing is carried out after the adhesive tape bonding the cut portion being peeled off.